Kidney stones, and also naturally-occurring stones in the bladder and the ureter can be exquisitely painful, and often require surgical relief. Excision or destruction of stones in the bladder and sometimes in the ureter can be relatively easily accomplished, but removal of stones from the kidney is a major procedure.
Surgical removal of stones from the kidney is a very serious and traumatic procedure. A large incision is made in the body. The kidney is essentially removed from the body and cut open. The stone or stones are then removed, whereupon the kidney is sutured and returned to the body with the body then being sutured. Typical recovery time is on the order of six to twelve months.
Chemotherapy is available as a noninvasive therapy for uric acid stones. In this therapy the urine is alkalized. The existing stone thus is dissolved over a substantial period of time, and in most cases the patient can be cured before this condition becomes acute. However the patient's condition is often already acute when the stone is discovered, and immediate removal is imperative. Attempts at chemical dissolution of other types of stones have not been successful.
More lately, extracorporeal distruction of kidney stones by means of lithotripters has become popular. With the use of earlier such machines as disclosed in Hoff et al U.S. Pat. Nos. 3,942,531 and Hausler 4,311,147 it has been necessary for the patient to be immersed in a tub of water in a crouched, face up position. Two dimensional x-ray procedures are utilized to determine the position of the stone by moving the patient. The machine includes an underwater spark gap shock wave generator which lies outside of the patient's body and at the first focus point of an ellipsoidal reflector. The patient is moved around in the water bath by several mechanisms until the kidney stone is positioned at the second focus point of the ellipsoid. A shock wave is then generated, and passes through the water bath and through the patient's body to convey the energy to the kidney stone. It will be apparent that precise aiming is necessary since the energy focused into an air or gas pocket in the body can cause damage to interface tissue, and in any event a misaimed shock wave has no effect on destruction of the kidney stone.
Some patients are reluctant to undergo x-ray aiming, and x-rays are not successful with certain types of stones that are not x-ray opague. Ultrasound devices have been used as an alternative as disclosed in Brisson, et al 4,763,652, assigned to the same assignee as the present application, namely Northgate Research Inc. of Arlington Heights, Ill. In accordance with Brisson et al, 4,763,652 the water bath is not necessary. A reflector is movable immediately adjacent to the body of the patient and is in contact with the patient's body through a diaphram, the reflector being filled with water. Ultrasound transducers are used to locate the kidney stone, and the transducers are connected through a computer to motors for positioning the reflector relative to the patient so that the kidney stone in the patient will lie at the second focus point of the reflector. This system works remarkably well, but skill is necessary to read ultrasound images properly.
There is, therefore, a demand for an aiming system for a lithotripter which requires minimal reading skill, so that substantially any physician or technician can properly position the ellipsoidal reflector relative to the patient.